1. Field of the Invention
The invention relates generally to a semiconductor process and, more particularly, to an integrated processing system for forming an insulating film used in thin film transistor liquid crystal display.
2. Description of the Related Art
The applications of thin film transistors (TFT) are numerous, more particularly in liquid crystal display (LCD) devices. LCD devices are known for their advantageous low operating voltages, absence of radiation, lightweight, and smaller dimensional size. As electronic appliances increasingly become portable and smaller, the use of TFT-LCD devices is therefore incumbent.
TFT-LCD usually includes an insulating film that is formed via a plasma enhanced chemical vapor deposition (PECVD) performed in a PECVD station. After the formation of the insulating film is completed, residual particles may deposit on the insulating film, which causes short-circuit through the insulating film and other types of failure of other components. A cleaning operation is therefore conventionally performed after the formation of the insulating layer on the substrate is completed to remove the residual particles. However, some residual particles may still remain after this traditional cleaning operation, and even if the residual particles are removed, they leave pinholes on the surface of the insulating film so that, consequently, it is not smooth. Because the back and forth movement of the substrate between the different cleaning and deposition stations is conventionally achieved by means of automatically or manually guided vehicles, the risk of pollution of the substrate by environmental contaminants is further increased.
An aspect of the invention is therefore to provide a method of forming an insulating film used in thin film transistor liquid crystal display and a processing station implementing the same method that can reduce the amount of residual particles on the insulating film. Thereby, failure and short-circuit of the insulating film are prevented and the yield is increased.
Another aspect of the invention is to provide a processing station that can reduce the conveyance time of the substrate being processed to form the insulating film.
To accomplish the above and other objectives, the invention respectively provides a method of forming a TFT-LCD insulating film that integrates deposition and cleaning operations and a processing station implementing the same method. The processing station comprises a chemical vapor deposition (CVD) unit in which the substrate is subjected to the deposition of a layer of insulating material, a cleaning unit in which the substrate is cleaned, a cassette station where a plurality of substrates are stored, and a transfer system for substrate conveyance. The substrates received in the cassette station are either substrates on standby to be processed to form an insulating film or substrates for which the formation of the insulating film is completed. The CVD unit is placed in a position facing the cassette station, the transfer system is disposed between the CVD unit and the cassette station, and the cleaning unit is positioned proximate to the transfer system. The relative disposition of the CVD unit, the cassette station, the cleaning unit and the transfer system is such that the transfer system is capable of conveying a substrate being processed between the cassette station, the CVD unit, and the cleaning unit.
To form a desired thickness of insulating film, a substrate is subjected to an operating cycle of the processing station as follows. The operating cycle includes a plurality of deposition passes, preferably two passes, alternated with at least a cleaning operation, and is performed until the desired thickness of the insulating film is obtained. Each deposition pass forms an intermediate thickness of insulating layer over the substrate that is smaller than the final thickness of the desired insulating film. Each cleaning operation, preferably wet cleaning, removes residual particles from an intermediary insulating layer. The conveyance of the substrate being processed between the cassette station, the CVD unit and the cleaning unit is achieved by means of the transfer system.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.